Wireless telegraphy.



J. HARDEN.

WIRELESS TELEGRAPHY.

APPLICATION FILED 0071210, 1904.

. 1,01 1,777. Patented Dec. 12, 1911.

MTNE'SSES 1 I [NS/ENTER ,M M Q JUHAMYES ZARD'N, 4 BY ATTYZ UNITEDsTArrEs PATENT OFFICE.

JOHANNES HARDEN, F SCI-IENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

WIRELESS TELEGRAIPHY.

Specification of Letters Patent.

Patented Dec. 12, 1911.

Application filed October 10, .1904. Serial No. 227,784.

To all whom it may concern:

Be it known that I, JoIIANNns Hlinor'm, a subject of the King of Swedenand Norway, residing at Schenectady, county of Schenectady, State of NewYork, have invented certain new and useful Improvements in \VirelcssTelegraphy, of which the following is a specification.

In the art of signaling by waves it is customary to provide the sendingapparatus with an aerial conductor or wire and to impress upon saidconductor an electromotive force of exceedingly high frequency. Thishigh frequency potential sets up high fre- 1 queney currents in theaerial wire which, from their inherent nature, give up their energy tothe surrounding space in the form of vibratory energy or etheralvibrations and these vibrations are in turn reconverted 2 intoelectrical vibrations at the receiving station. In such systems thepower of the sending apparatus and the sensibility of the receivingapparatus are dependent to a great extent on the relation between the 2natural period of vibration of the aerial conductors and the frequencyof the oscillating current used in the system. Thus if e aerial at thesending station has a natural period of vibration ofthe same fre- 3quency as the impressed oscillation or a harmonic of such frequency itwill convert the energy of the oscillating charge into etherealvibrations with an efficiency much higher than that attainable when thisresonance of the aerial does not exist. To conveniently secure resonanceof the sending aerial I provide an adjustable condenser and anadjustable inductance in series with it. To determine the exactadjustment of these regulators for a condition of resonance I use asmall adjustable spark gap in the aerial wire. The discharge across thistest spark gap will be a maximum when resonance of the circuit has beenattained.

In wireless telegraphy apparatus, it has heretofore been customary toprovide the sending and receiving apparatus with aerial conductorsconsisting of a single wire or of a group of wires connected together atone end, but in my improved apparatus I make use of a substantiallyclosed loop of one or more turns and thereby secure a marked improvementin the power and sensibility of the apparatus.

My invention also relates to an improved apparatus for producing a sparkdischarge, and to certain other details of construction and arrangementwhich are more particularly set forth in the appended claims.

When a single aerial Wire is used at the sending station each dischargeof energy from the wire takes place in an exceedingly short time and inconsequence there is transmitted through the ether a quantity of energyhigh in potential or intensity but of very short duration. The result isthat when this energy reaches the coherer its effect thereon is of suchshort duration that the coherer and parts allied therewith sometimes donot have time to operate before the entire flow of energy has takenplace.

By the use of a'erials in the form of loops I am able to spread eachdischarge over a considerable time interval and thus give the coherersuflicient time to act. This increase in the time interval is probablydue to surging of the current in the aerial loops after the originalcharging oscillations, caused by the spark discharge, have ceased; thesurging being due in part to the resonant condition of the circuits andin part to oscillations of the magnetic flux threading the loops. Thismagnetic flux serves in a sense as a reservoir to store up part of theenergy of the spark discharge which is later given out in rhythmicoscillations on the aerial thus converting into useful etherealvibrations the magnetic energy set up by the current from the originalspark discharge.

In the drawing, Figure 1 represents one form of sending apparatus withmy improved form of aerial conductor; Fig.2 is a modification of asending apparatus in which a direct-current generator is used as the.source of energy and in which the rapid oscillations are obtained bymeans of a mercury vapor spark gap operating in conjunction withcondensers.

Energy for the excitation of the aerial may be derived from any suitablesource such as an induction coil or an alternating current dynamo but Iprefer to use the arrangement shown in Fig. 2 in which a direct currentdynamo is used to charge condensers which in turn discharge through ararefied atmosphere. This latter arrangement gives a higher efliciencyand also a higher speed of operation than I have been able to. attainwith other sourcesof energy.

When an alternating current dynamo is used I prefer the arrangementshown in Fig. 1. The dynamo 1, driven 1n any convenient manner, suppliespower to the primary or low pressure side 2 of a transformer, thesecondary 3 or high pressure side of which supplies energy to thesending apparatus. A key 2 serves to close the dynamo circuit at properintervals for transmitting signals of the Morse code. The alternator mayoperate at commercial frequencies as for instance 60 cycles per secondand at a potential of 110 volts. quency of 60 cycles is of course toolow to be effective in setting up ethereal vibrations and to secure thedesired high frequency I preferbly employ an adjustable spark gap atlocated between the terminalsof the high potential coil 3 of the step uptransformer. Condensers 5 and 6 are located in the conductors connectingthe spark gap 4 with the aerial loop 7. These condensers are renderedadjustable in capacity by the segmental switches 8 and 9 which serve toincrease or decrease the number of condenser plates in circuit. Areactance coil 10 connects one end of the aerial loop 7 to groundthrough the ground conductor 10 and a movable contact 11 serves to varythe proportion of reactance coil 10 between the aerial loop and thelocal circuit which includes the condensers 5 and 6. The other side ofthe loop 7 is connected to the local condenser circuit through the testspark gap 12. In adjusting the aerial loop to the condition of resonancethe reactance coil 10 and the condensers 5 and 6 are adjusted until amaximum discharge is obtained across spark gap 12 in which condition theeffective vibratory length of the aerial loop is equal to one quarterwave length of the impressed vibrations and the conversion of electricalenergy into ethereal vibrations is most eflicient. Not only is this truebut with the line in this condition the flow of current in the aerial isat its maximum and hence the magnetic efiect set up thereb is also atits maximum. This magnetic e ect consists of a flux at right angles tothe plane of the loop which flux reverses at each reversal of thecurrent in the aerial and serves to prolong the period during whichethereal vibrations are given off from the aerial and which alsoultimately gives up a large part of its magnetic energy as electricalenergy in the form of current oscillations in the aerial loop after theoriginal spark discharge has ceased. After the condition of resonancehas once been obtained the spark gap 12 is adjusted so that no dischargetakes place at this point when the apparatus is in actual .use fortransmitting messages. This may be accomplished by shunting the sparkgap by a switch 13.

In Fig. 2, I have shown the arrangement which I prefer to use when theenergy is A fre-' derived from a direct-current source. Thedirect-current dynamo 14:, driven in any suitable manner, is connectedto a vacuum spark gap apparatus 15 through a sending key 16 and avariable reactance 17. Adjustable condensers 18 and 19 are connectedbetween the terminals of the spark gap and the sending aerial 20.

l/Vhile I may use for the vacuum spark gap a mercury vapor lamp ofordinary construction I have found that such an arrangement is notentirely. satisfactory as the a lamp tube becomes coated on the insidewith a dark deposit which in time forms a short circuit from oneelectrode to the other thus rendering the tube useless. This darkdeposit I, believe to be due to a partial decomposition or similarchange of the glass surface produced by the action of the spark. I havemade the important discovery that if the electrodes are inclosed insilica tubes this deposit does not form and I am able to use spark gapsof this improved construction for a long time without material de--preciation. The vacuum chamber 21, which may be of glass or similarmaterial, incloses the two mercury electrodes 22 and 23 and maintains ararefied atmosphere about them. Silica tubes or cups 24 and 25 surroundthese mercury electrodes and protect the glass walls of the chamber 21from the destructive action of the spark which passes between the twomercury electrodes. As it is impossible to satisfactorily fuse thesilica cups to the glass vacuum chamber I support the cups by means of aglass standard 26 fused to the base of the vacuum chamben and providedat its top with a hook whicfi engages a solid silica rod 27 joining thetwo silica tubes or cups 22, 23. Projections 28 on the inner walls ofthe vacuum chamber serve to further steady and support the silica cups.

I am aware that mercury vapor spark gaps have been used on alternatingcurrent circuits to produce an oscillating discharge, but a considerableincrease in efficiency and rapidity of operation is obtained by usingdirect current. The aerial and its grounded reactance coil and testspark gap are similar to the corresponding parts in Fig. 1.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. In a system of wireless telegraphy, the combination of a sendingaerial in the form of a substantially closed loop traversed in series byoscillations, an inductive reactance in series therewith, a capacityreactance in series with said inductive reactance, a source of energyconnected in series with said capacity and said series connected loop.and a ground connection for said aerial between said inductive reactanceand said capacity reactance.

2. In a system of wireless telegraphy, the

combination of an aerial in the form of a substantially closed 100 anadjustable inductive reactance in series therewith, a test spark gap inseries therewith, means for short circuiting said spark gap, a secondspark gap for setting up high frequency oscillations, and an adjustablecapacity reactance connectin each side of said second spark gap to saidaerial.

3. In a system of wireless telegraphy, the combination of a sendingaerial in the form of a substantially closed loop, a capacity reactancein series therewith, a spark gap shunting said aerial and adapted toproduce high frequency oscillations traversing said looped circuit inseries, and a source of current connected across said spark gap and inseries with said aerial.

4. A spark gap apparatus comprising a plurality of mercury electrodesbetween which a spark discharge may pass, means for maintalning ararefied atmosphere about said electrodes and a silica cup surroundingone of said electrodes.

5. The combination with a source of energy, of a s ark gap apparatushaving a gas tight cham er, mercury electrodesin said chamber betweenwhich a spark may pass, and means inclosing said electrodes forprotecting the walls of said chamber from the destructive action of saidspark.

\ 6. The combination with a source of direct current, of a vacuum sparkgap apparatus having a (gas tight chamber of glass, mercury electro esin said chamber between which a spark may pass, and a silica tubeinclosing each of said mercury electrodes to protect the inner surfaceof the glass from the destructive action of said spark.

7. In a system of wireless telegraphy, th combination of a source ofdirect current, a vacuum spark gap connected across said source, anaerial connected in series with said source and shunting said spark gap,and a plurality of condensers connected in series with said aerial andwith said series connected source thereby constituting a looped seriescircuit traversed by oscillations.

8. The combination with a source of current, of a spark gap apparatushaving a gas tight chamber, mercury electrodes in said chamber betweenwhich a spark may pass, and a silica cup inclosing each of saidelectrodes and separating it from the wall of said gas-tight chamber.

9. In a system of wireless telegraphy, the combination of a sendingaerial in the form of a substantially closed loop traversed in series byoscillations, an inductive reactance in series therewith, a capacityreactance in series with said inductive reactance, a source of energyconnected in series with said capacity reactance and in series with saidaerial, a spark gap in shunt with saidsourc-e and a ground connectionfor said aerial.

In witness whereof, I have hereunto set my hand this seventh day ofOctober, 1904.

JOHANNES HARDEN. Witnesses:

EDWARD WILLIAMs, Jr., YHELEN Onrono.

